Buy American Act for Construction Materials

A client asked the following question, and I am seeking the benefit of Wifcon members/guests with the same topic:

Contractor A is the Prime on a DOD construction contract taking place in the ME

Subcontractor 123 has proposed, and is using, billing & being paid for certain foreign construction materials under an exception to the Buy American Act

Subcontractor 987 (Client) proposed the same foreign construction materials, however they have been told by the contracting officer that they cannot have a waiver.

As a practical matter, I am under the impression that the government would have a contractual relationship with the Prime, and that the Subcontractors would have a similar relationship with the Prime.

The client's question was: if the other subcontractor can be paid for the foreign materials then why couldn't they be granted a similar exception? It is established that the materials in question are not available from any American sources, and they are going to have to "eat" the cost of these materials in order to fulfill their obligations under the subcontract, unless they are allowed to have an exception under the Buy American Act.

Any help would be greatly appreciated.